This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. SAXS will be applied to understand the assembly and disassembly of Hepatitis B virus (HBV) cores (non-infectious virus-like particles produced from E. coli expressed protein) and to investigate the mechanism of anti-viral drug-induced core particle disruption. HBV is a major pathogen and one of the most prevalent causative agents of cancer in humans. While effective vaccines are available, it remains of significant interest to add to the battery of antiviral therapeutics that can combat the virus. The goal of the studies is to understand mechanistically how a complex viral assembly is constructed and how capsid-targeted drug compounds can shunt the assembly reactions off-pathway. We recently studied the capsid disassembly process which exhibited a distinct kinetic profile predicted by computational models. We also conducted static x-ray scattering measurements of the capsid protein as a function of urea concentration prior to planned time-resolved measurements. We have been able to determine that the capsid protein can be kept unassembled in the dimeric form in the presence of 50 mM for a few days or longer. In the next step, we plan on conducing time-resolved studies of assembly induced a salt concentration jump via a rapid stopped-flow mixing. We anticipate to observe initial steps of the capsid assembly as a function of time and study the effects of potential drug compounds modifying assembly kinetics in near future.